Cyclone-type collectors are well known in the art, including types having particle skimming means, and inlet scrolls or volutes. Further, it is known to provide cyclone-type collectors with means in the clean gas outlet tube to improve the particle collecting efficiency of the collector. Exemplary of such prior art are U.S. Patents:
U.S. Pat. No. 1,344,146-Peck PA0 U.S. Pat. No. 1,408,693-Deily PA0 U.S. Pat. No. 2,074,818- Watson PA0 U.S. Pat. No. 2,583,696-Held et al.